The present invention relates to an automatic chemical analyzer.
In an automatic chemical analyzer used in clinical examinations and the like, analysis is automatically performed as follows. Serum (i.e., a sample) taken from a patient as an analysis object is mixed, for reaction with a reagent corresponding to a desired analysis item. (The reagent is diluted, if necessary, before and/or after the sample is mixed with the reagent.) Light transmission through the reaction solution is measured so as to obtain an absorbancy. Alternatively, a potential difference between electrodes appropriately arranged in the reaction solution may be measured. The absorbancy or the electrode potential is compared with a calibration curve obtained, in advance, from the corresponding reagent and a standard substance, e.g., a standard serum, to thereby obtain a concentration of a specific component of the sample corresponding to either the absorbancy or the electrode potential.
In general, even if a reagent is kept at a low temperature of about 2.degree. to 8.degree. C., which is considered a preferable condition, reagent deterioration is evident. That is, since the reagent contains a plurality of drugs, characteristics of the reagent are degraded due to, e.g., reaction between the mixed drugs, resulting in poor measurement precision. For this reason, formation of a calibration curve using the standard serum (i.e., calibration) must be repeated at predetermined intervals.
However, in the automatic chemical analyzer, a number of analysis items are present, and reagents used in examinations for respective items exhibit various degradation speeds. For this reason, an interval (i.e., a "calibration interval") from an immediately preceding calibration curve to the next calibration is varied in accordance with the types of reagent, i.e., measurement items. In the conventional automatic chemical analyzer, calibration for each analysis item is not of particular concern. For example, when two analysis items having respective calibration intervals of 3 hours and 1 hour are present, calibration is performed at intervals of 1 hour even for the analysis item having the calibration interval of 3 hours. In this manner, when calibration is performed too frequently, much expensive standard serum and sample material are wasted, resulting in high cost. Similarly, a sample line conveying a reaction chamber for effective processing must be stopped for every calibration, thus wasting time.
In the conventional automatic chemical analyzer, since a calibration timing depends upon the judgment of an experienced clinician, an error in measurement precision can easily occur due to the difference in calibration timing of each clinician who must perform a predetermined operation at constant intervals for accurate calibration.
In order to calibrate an analysis item having a relatively short calibration interval, processing can be performed wherein an analysis item having a relatively long calibration interval is not calibrated. However, in order to realize such processing, the calibration interval for each analysis item must be stored, and calibration and other controls must be performed for each item, thus complicating the processing sequence and apparatus arrangement. For this reason, it is difficult to realize such processing in practice.